International and national assessments suggest that U.S. students' mathematics performance declines drastically as they progress to higher grades. Reforms to improve student math achievement and math curriculum have not yielded the hoped-for outcomes because improving math performance demands more systematic changes in how math teachers are equipped at the preservice and in-service levels. Research advances on the expertise needed in mathematics teaching have identified distinct knowledge and skills math teachers need. Policies to ensure that teachers and teacher candidates are equipped with this knowledge and these skills is the most viable solution to the nation's ongoing problem with math learning. Providing a system of supports to overcome teachers' reliance on implicit biases could also help erase inequity in math instruction and close the performance gap of students from different groups.